The present invention relates to a lift-table flatcar conveyor.
The invention also relates to a method for transferring rolls or roll groups by means of a lift-table flatcar conveyor.
Rolls coming from a papermaking machine are slit at a slitter-winder into rolls of narrower width according to customer order, followed by packaging of the rolls at a packaging machine. During the packaging operation, the roll ends are first provided with inner headers and next a sufficient number of convolutions of a wrapper material is wound about the roll on the wrapper station of the packaging machine, whereupon the overlap portion of the wrapper is draped over the inner headers placed on the roll ends. In some instances, a number of wrapper material convolutions is first wound about the roll, followed by the insertion of the inner headers into the tubes formed by the wrapper overlap at the roll ends and the wrapper rims are next draped over the inner headers. Generally, an outer header is attached by hot-melt glueing onto the draped wrapper rim and the inner header at the end platen press of the packaging machine.
The widths of the narrowest customer rolls coming from the slitter to the packaging machine vary in the range of 100-500 mm. For instance, in mills making fine paper grades, the roll widths of narrow rolls are typically from 180 mm to 400 mm, in cardboard mills from 350 mm to 500 mm and in the manufacture of roll cores from 100 mm to 300 mm. Narrow rolls are packed either individually wrapped or, typically, as two- or multi-roll packs containing 2-4 rolls bunched end-to-end. The customer rolls to be packaged in two- and multi-roll packs are normally wrapped together immediately after they leave the slitter, because their handling and carrying in bundled form is much easier.
The rolls to be packaged can be transferred from one station of the packaging machine to another using a lift-table conveyor in which a single roll or a group of rolls is placed on a flatcar that moves backward and forward along a long track between two successive stations of the packaging machine. Herein, a roll resting on the support rolls of the first station is moved uphill along the track and by way of lifting up the platform table of the flatcar, whereupon the roll can be moved to the second station on the flatcar. Subsequently, the roll is delivered onto the support rolls of the second station by lowering both the track and the platform table. Finally, the flatcar is returned to the first station to fetch the next roll. The roll being transferred is placed on the flatcar so that the center axis of the roll is aligned parallel to the travel direction of the flatcar, which means that the roll can readily topple when the flatcar accelerates or decelerates its speed. The risk of roll toppling is particularly imminent when narrow rolls are being transferred by fast conveyors. It may also happen that narrow rolls at the ends of a roll group fall sideways during the transfer operation. Obviously, the problem can be eliminated by reducing the acceleration or deceleration rate of the flatcar units. This, however, also reduces the throughput capacity of the roll packaging machine.
It is an object of the present invention to provide an entirely new type of lift-table flatcar conveyor and a method for transferring rolls or roll groups on a lift-table flatcar conveyor so that the above-mentioned complications are overcome.
The goal of the invention is achieved by way of providing the lift-table flatcar conveyor with support means such as support arms that support the roll or roll group being transferred and keep the same upright during the transfer operation. The support arms are arranged to press against both ends of the roll or roll group during transfer. During the return travel of the conveyor flatcar, the support means are rotated into a home position, wherein they can move without the risk of a physical contact past rolls or roll groups resting on the stations of the packaging machine. Advantageously, the home position of the support arms is such that the arms are rotated downward in a position parallel to the tracks, whereby the arms can travel below the rolls resting on the stations at a level which is lower than that on which the rolls are resting. Further advantageously, the support means are integrated with the construction of the lift-table flatcar traveling between the stations of the packaging machine.
More specifically, the lift-table flatcar conveyor according to the invention is characterized by what is stated in the characterizing part of claim 1.
Furthermore, the method according to the invention for transferring rolls or roll groups on a lift-table flatcar conveyor is characterized by what is stated in the characterizing part of claim 8.
The invention offers significant benefits.
By virtue of the invention, the capacity of a roll packaging machine increases substantially because rolls can be transferred without the risk of toppling at an increased speed between the stations of the packaging machine. A lift-table flatcar conveyor according to the invention is capable of safely transferring in an upright position rolls about 150 mm wide, while transfer systems lacking support means can transfer at a comparable speed only rolls having a width of about 400 mm or wider. During the return travel of the conveyor flatcar, the support arms are arranged to move past the rolls or roll groups resting on the stations of the packaging machine. Advantageously, the home position of the support arms is such that the arms are rotated downward in a position parallel to the tracks, whereby the arms can travel below the rolls resting on the stations at a level which is lower than that on which the rolls are resting and, thus, do not need any clearance to be provided on the sides of the conveyor track. Moreover, the support means according to the invention have a simple construction and can be retrofitted on existing lift-table flatcar conveyor, too.